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- Vision begins when light rays are reflected off an object and enter the eyes through the cornea (the transparent outer covering of the eye)
- The cornea bends the rays so they pass through the pupil
- The iris, or coloured portion of the eye that surrounds the pupil, opens and closes (making the pupil bigger or smaller) to regulate the amount of light entering the eye
- The light rays then pass through the lens, which actually changes shape so it can further bend the rays and focus them on the retina
- The retina is a thin layer of tissue at the back of the eye that contains millions of tiny light-sensing nerve cells called rods and cones because of their distinct shape
- Cones are concentrated in the centre of the retina, in the macula. In bright light conditions, cones provide clear, sharp central vision and detect colours and fine details
- Rods are located outside the macula and extend to the outer edge of the retina, providing peripheral vision, allowing the eyes to detect motion and helping us see in dim light and at night
- These cells in the retina convert the light into electrical impulses. An image is produced when the optic nerve sends these impulses to the brain
- Close up objects are clear, but long distance objects become blurry
- Occurs when the eye is too long in relation to the curvature of the cornea
- Light rays don't focus on the retina, but in front of it
- You can see things in the distance but have trouble up close
- Occurs when the eye is too short in relation to the curvature of the cornea
- Light rays focus behind the retina
- The cornea is irregular in shape
- You generally see all objects, near or far, with distortion, creating an uneven image because of the unequal bending of light rays entering the eye
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